1. Field
Exemplary embodiments of the present invention relate to a light detection device; and, particularly, to a light detection device having improved light detection efficiency by growing a single crystal porous zinc oxide (ZnO)-based oxide semiconductor layer on a substrate in accordance with an Metal-Organic Chemical Vapor Deposition (MOCVD) method.
2. Discussion of the Background
Ultraviolet light is invisible to the human eye because it falls outside the visible spectrum. Ultraviolet light is a generic term for electromagnetic radiation having a wavelength range of about 397 nm to 10 nm. Ultraviolet light having a very short wavelength may be indistinguishable from X-ray radiation. Furthermore, infrared light may be called heat rays, whereas ultraviolet light may be called actinic rays because they have a strong chemical action.
Ultraviolet light having a wavelength of 400 nm or less may be classified into several wavelength bands. A UV-A region light has a wavelength range of 320 nm to 400 nm, and 98% or more of UV-A region of solar light may reach the surface of the earth. The UV-A region light may affect a darkening or ageing phenomenon on human skin. A UV-B region light has a wavelength range of 280 nm to 320 nm, and only 2% of the UV-B region of solar light may reach the surface of the earth. The UV-B region light may have a very serious influence on the human body, such as contributing to skin cancer, cataracts, and a red spot phenomenon. A representative value of quantified influences of UV light on the human body is a UV index defined by the amount of incident UV-B region light.
Most of the UV-B region light may be absorbed by the ozone layer, but the amount of the UV-B region light that reaches the surface of the earth may increase, and an area reached by the UV-B region light may also increase, owing to the recent destruction of the ozone layer. This may raise a serious environmental problem.
A UV-C region light has a wavelength range of 200 nm to 280 nm, and the UV-C region rarely reaches the surface of the earth because almost the entire UV-C region of solar light may be absorbed in the atmosphere. The UV-C region light may be chiefly used in a sterilization action.
A device capable of detecting UV light includes a Photo Multiplier Tube (PMT) and a semiconductor device. The semiconductor device may be commonly used because it may be cheaper than the PMT and may also be smaller in size than the PMT.
The semiconductor device may be made of gallium nitride (GaN), silicon carbide (SiC), or zinc oxide (ZnO) having a wide bandgap. From among them, ZnO are materials may have a wide energy bandgap of 3.3 eV, high exciton binding energy of 60 meV in room temperature, and excellent optical characteristics. Furthermore, the energy bandgap of ZnO may be easily controlled by adding Mg or Cd.
In the prior art, in order to grow ZnO, a sputtering method or a Pulsed Laser Deposition (PLD) method capable of implementing high oxygen partial pressure may be chiefly used.
However, a ZnO layer grown using the conventional sputtering or PLD method may be problematic in that the binding force of crystals is low because sufficient thermal energy is not supplied when growing the ZnO layer and thus device characteristics may be deteriorated.